The disclosure relates generally to time-division duplexed (TDD) communications, and more particularly to automated determination of threshold power level for use in distinguishing between downlink and uplink states in TDD configurations communications.
Wireless communications is rapidly growing, with ever-increasing demands for high-speed mobile data communication. As an example, local area wireless services (e.g., so-called “wireless fidelity” or “WiFi” systems) and wide area wireless services are being deployed in many different types of areas (e.g., coffee shops, airports, libraries, etc.). Time-division duplexed (TDD) communications is one type of wireless communications that is being employed for high-speed mobile communications. Known examples of TDD include Digital Enhanced Cordless Telecommunications (DECT) wireless telephony, and TD-code Division Multiple Access (CDMA) (TD-CDMA). TDD refers to providing duplex communications links whereby downlink communications signals are separated from uplink communications signals by the allocation of different time slots in the same frequency band. TDD allows both downlink and uplink communications transmissions to share the same transmission/communications medium. More specifically, TDD involves dividing a data stream into data frames and assigning different time slots to downlink and uplink communications transmissions. Users in a TDD communications system are allocated time slots for downlink transmissions and uplink transmissions. TDD also advantageously allows for asymmetric assignment and flow for uplink and downlink data transmissions in TDD data frames to provide for asymmetric (i.e., different) capacities or data rates between downlink communications and uplink communications depending on traffic and throughput considerations.
TDD can be employed in distributed communications systems (DCSs) to separate downlink communications signals from uplink communications signals by matching full duplex communications over a half-duplex communications link. For example, a DCS may be a distributed antenna system (DAS) that has a series of distributed antennas forming remote coverage areas for distributing downlink and uplink communications signals between a signal source and client devices. TDD DCSs communicate with TDD wireless devices called “clients,” “client devices,” or “wireless client devices,” which must reside within the wireless range or “cell coverage area” in order to communicate with an access point device. TDD DCSs may be particularly useful to be deployed inside buildings or other indoor environments where TDD client devices may not otherwise be able to effectively receive radio-frequency (RF) signals from a source, such as a base station for example. Exemplary applications wherein TDD DCSs can be used to provide or enhance coverage for wireless services include public safety, cellular telephony, wireless local access networks (LANs), location tracking, and medical telemetry inside buildings and over campuses.
One approach to deploying a TDD DCS involves the use of RF antenna coverage areas, also referred to as “antenna coverage areas.” Antenna coverage areas can be formed by remotely distributed antenna units, also referred to as “remote units (RUs).” The remote units each contain or are configured to couple to one or more antennas configured to support the desired frequency(ies) or polarization to provide the antenna coverage areas. Antenna coverage areas can have a radius in the range from a few meters up to twenty meters as an example. Combining a number of remote units creates an array of antenna coverage areas. Because the antenna coverage areas each cover small areas, there typically may be only a few users (clients) per antenna coverage area. This arrangement generates a uniform high quality signal enabling high throughput supporting the required capacity for the wireless system users.
In TDD DCSs where data is transferred in sequential synchronized radio frames, it may be required to determine periods when downlink communications signals and uplink communications signals are being transmitted in a given time slot in the TDD frame since TDD allows both downlink and uplink communications transmissions to share the same transmission/communications medium. Transmitter and receiver circuits in such a TDD DCS must be synchronized to these downlink communications signal and uplink communications signal periods so that downlink communications signals are not transmitted when uplink communications signals are present on the communications medium, and vice versa. In other words, the radio frame structure is known to TDD communications devices in the TDD DCS. Such TDD communications devices know when uplink communications messages can be sent and when uplink communications messages should not be sent to receive downlink communications signals. Otherwise, data losses can occur when downlink communications signals are not received when uplink communications signals are being transmitted. “Back-off” collision detection and avoidance systems can be employed to wait for a defined period of time until the communications medium is clear of uplink communications signals before asserting new downlink communications signals on the communications medium. However, throughput would be reduced to half-duplex as a result. Collision detection and management mechanisms may also add design complexity, thereby increasing cost by requiring additional components, and requiring additional area on electronic boards.
No admission is made that any reference cited herein constitutes prior art. Applicant expressly reserves the right to challenge the accuracy and pertinency of any cited documents.